Frequency comparator utilizing enveloping-event detection via symbolic dynamics of fixed or modulated waveforms
View Patent ↗Systems, algorithms, circuits, and methods for pattern detection of signature events in signal dynamics defined by instantaneous states of applied square-wave signals. Selected patterns may be recognized individually or in equivalence classes, and detection may be implemented via state or transition analysis. Varieties of conditions may be detected in parallel, including phase, ambiguity states, and frequency comparison. One embodiment realizes a real-time frequency comparator for asynchronous square-wave signals. Realizations detect various classes of symmetry conditions unique to enveloping events occurring for these classes of square-wave signal pairs. This approach provides feedback-free implementations operating over an extremely wide frequency range and does not require signals of quadrature form. A typical logic circuit implementation involves two to four flip-flops, or two-stage two-bit shift registers, and modest combinational logic. The resulting system can be readily implemented as a utility integrated circuit of modest scale or as a small-scale “IP core” within larger system-on-a-chip (SoIC) devices.
1. A method for comparing frequency performed by a processor, the method comprising:
detecting transitions of a first input waveform;
detecting transitions of a second input waveform; and
identifying a first faster input waveform as a waveform of the first and second input waveforms which exhibits a plurality of transitions that occur between two consecutive transitions of the other of the first and second input waveforms.
2. The method according to claim 1 , wherein at least one of the first and second input waveforms comprise a pulse waveform.
3. The method according to claim 2 , wherein the pulse waveform comprises periodic behavior for the interval of time and has a duty cycle of effectively 50%.
4. The method according to claim 3 , further comprising:
driving a first divide-by-two counter with a third input waveform to produce the first input waveform; and
driving a second divide-by-two counter with a fourth input waveform to produce the second input waveform.
5. The method according to claim 4 , wherein each of the third and fourth input waveforms comprises a pulse waveform.
6. The method according to claim 5 , further comprising:
identifying a second faster input waveform as a waveform of the third and fourth input waveforms which exhibits a plurality of transitions that occur between two consecutive transitions of the other of the third and fourth input waveforms.
7. The method according to claim 6 , wherein at least one of the third and fourth input waveforms comprise periodic behavior for an interval of time.
8. The method according to claim 7 , wherein either the third input waveform or the fourth input waveform comprises an asymmetric pulse waveform, wherein the periodic behavior comprises a duty cycle effectively different than 50%.
9. The method according to claim 2 , further comprising:
defining a first set of four combinations of consecutive transitions of the first input waveform as occurring during a period of time during which the second waveform does not transition;
defining a second set of four combinations of consecutive transitions of the second input waveform as occurring during a period of time during which the first waveform does not transition; and
determining a frequency relationship between the first and second input waveforms based upon the first and second sets.
10. The method according to claim 9 , further comprising:
defining a first subset of the first and second sets, wherein an event from the first subset indicates that the first input waveform is faster than the second input waveform; and
defining a second subset of the first and second sets, wherein an event from the second subset indicates that the second input waveform is faster than the first input waveform.
11. The method according to claim 10 , further comprising:
identifying an asymmetric attribute of least one of the first input waveform and the second input waveform responsive to detecting a subset of combinations of the first and second sets occurring in a temporal sequence.
12. The method according to claim 9 , wherein at least two combinations of the first and second sets occur in a temporal sequence, the method further comprising:
identifying the first faster input waveform based upon a subset of combinations occurring in the temporal sequence.
13. The method according to claim 1 , further comprising:
driving a first comparator with a third input waveform to produce the first input waveform; and
driving a second comparator with a fourth input waveform to produce the second input waveform.
14. The method according to claim 13 , wherein at least one of the third and fourth input waveforms comprises a non-pulse waveform.
15. The method according to claim 1 , further comprising:
detecting transitions of a third input waveform; and
identifying a second faster input waveform as a waveform of the first, second, and third input waveforms which exhibits a plurality of transitions that occur between two consecutive transitions of the other waveforms of the first, second, and third input waveforms.
16. The method according to claim 1 , further comprising:
detecting transitions of a third input waveform;
detecting transitions of a fourth input waveform;
identifying a second faster input waveform as a waveform of the third and fourth input waveforms which exhibits a plurality of transitions that occur between two consecutive transitions of the other of the third and fourth input waveforms; and
identifying a third faster input waveform as a waveform of the first and second faster input waveforms which exhibits a plurality of transitions that occur between two consecutive transitions of the other of the first and second faster input waveforms.
17. A frequency comparator, comprising:
a detector configured to detect transitions of a first input waveform and transitions of a second input waveform; and
a circuit configured to identify a first faster input waveform as a waveform of the first and second input waveforms which exhibits a plurality of transitions that occur between two consecutive transitions of the other of the first and second input waveforms.
18. The frequency comparator according to claim 17 , wherein at least one of the first and second input waveforms comprise a pulse waveform.
19. The frequency comparator according to claim 18 , wherein the pulse waveform comprises periodic behavior for the interval of time and has a duty cycle of effectively 50%.
20. The frequency comparator according to claim 19 , further comprising:
a first divide-by-two counter driven by a third input waveform to produce the first input waveform; and
a second divide-by-two counter driven by a fourth input waveform to produce the second input waveform.
21. The frequency comparator according to claim 17 , further comprising:
a first comparator driven by a third input waveform to produce the first input waveform; and
a second comparator driven by a fourth input waveform to produce the second input waveform.
22. The frequency comparator according to claim 17 , further comprising:
defining a first set of four combinations of consecutive transitions of the first input waveform as occurring during a period of time during which the second waveform does not transition;
defining a second set of four combinations of consecutive transitions of the second input waveform as occurring during a period of time during which the first waveform does not transition; and
determining a frequency relationship between the first and second input waveforms based upon the first and second set.
23. The frequency comparator according to claim 22 , wherein the circuit is further configured to:
identify an asymmetric attribute of least one of the first input waveform and the second input waveform responsive to detecting a subset of combinations of the first and second sets occurring in a temporal sequence.
24. The frequency comparator according to claim 22 , wherein at least two combinations of the first and second sets occur in a temporal sequence, and wherein the circuit is further configured to:
identify the first faster input waveform based upon a subset of combinations occurring in the temporal sequence.
25. The frequency comparator according to claim 17 , wherein the circuit is further configured to:
detect transitions of a third input waveform; and
identify a second faster input waveform as a waveform of the first, second, and third input waveforms which exhibits a plurality of transitions that occur between two consecutive transitions of the other waveforms of the first, second, and third input waveforms.
26. The frequency comparator according to claim 17 , wherein the circuit is further configured to:
detect transitions of a third input waveform;
detect transitions of a fourth input waveform;
identify a second faster input waveform as a waveform of the third and fourth input waveforms which exhibits a plurality of transitions that occur between two consecutive transitions of the other of the third and fourth input waveforms; and identify a third faster input waveform as a waveform of the first and second faster input waveforms which exhibits a plurality of transitions that occur between two consecutive transitions of the other of the first and second faster input waveforms.
27. A method for comparing frequency implemented as a utility integrated circuit, the method comprising:
detecting transitions of a first input waveform;
detecting transitions of a second input waveform; and
identifying a first faster input waveform as a waveform of the first and second input waveforms which exhibits a plurality of transitions that occur between two consecutive transitions of the other of the first and second input waveforms,
wherein the first input waveform is produced by driving a first divide-by-two counter with a third input waveform, and the second input waveform is produced by driving a second divide-by-two counter with a fourth input waveform, and
wherein at least one of the first and second input waveforms comprises a pulse waveform having a periodic behavior for the interval of time and a duty cycle of effectively 50%.